Thunder Bay

Explosion halts work on High Street retaining wall in Thunder Bay, Ont.

Work to replace the retaining wall at High and Cornwall streets in Thunder Bay, Ont., has been temporarily halted due to an explosion at the construction site.

Explosive device likely left over from previous construction projects, city says

Work to replace the 70-year-old retaining wall on High Street in Thunder Bay has been halted following an explosion at the site. (Thunder Bay Culture & Events / Facebook)

Work to replace the retaining wall at High and Cornwall streets in Thunder Bay, Ont., has been temporarily halted due to an explosion at the construction site.

The explosion occurred Tuesday afternoon, when an old, undiscovered explosive device was accidentally detonated by a worker using a breaker, essentially a large jackhammer mounted on an excavator. There were no injuries.

Experts to assess site

Work was immediately stopped and won't resume until demolitions experts can assess the site.

"We're assuming it's from some previous construction," Mike Vogrig, project engineer with the City of Thunder Bay, told CBC. "It's the first time I've encountered anything like this."

"I know they've always used explosives for rock removal," he said. "I know the bedrock there is very hard, so it could've been when they were building the road. When they were originally building the retaining wall, there could've been some blasting."

No blasting is taking place at the site as part of the current project, the city said in a media release issued Wednesday. All rock removal is being done via mechanical means.

Whether any more such devices are on the site is unknown. That will be determined as part of the assessment, which will be done by demolitions experts from Ottawa company Explotech. They could be in the city as early as today, Vogrig said.

Nearby homes shook

And while, as far as the city knows, the blast didn't cause any damage to surrounding homes, the explosion was large enough to shake them, Vogrig said.

"Likely moving forward now, we're probably going to do a post-incident survey of maybe five-to-six houses that were close to where the blast was," he said. "We know visually, from the outside, that we have no broken windows, no visible damage that we can see at this point in time."

The Ontario Ministry of Labour has been notified about the incident, Vogrig said.